This is my yappy place. Sometimes I share my workshop experiences in jewelry-making; sometimes I talk about other things that interest me. I have created tabs along the top of my blog (next to the word home, below this msg) so you can select certain categories if you like.

header info

Pages

Sunday, October 27, 2013

I Begin the Metal Clay Firing Tests in Earnest and An Online Free Calculator for Metal Clay Ring and Pendant Sizing

I decided to go back to square one and run some tests.My intuition (and a few isolated incidences)
tells me some of my larger pieces may be only sintered superficially.

I think if I find the lowest temperature at which the piece
appears to be sintered, the inside could still be very unsintered and therefore
pose a potential problem in the long run.

So I want to know what’s the highest temperature I can fire
at without showing signs of over-firing.

The test I do for sintering is to sand the piece.But this could only be showing me that the
outside of the piece is sintered.

I recently had a two-part (onlay) piece that was, to all
appearances, fully sintered.I sanded it
(120, 240, 400) then polished it and gave it a patina.

A few days later, the onlay fell off,
revealing unsintered clay on both halves of the piece.

I’ve decided to do some tests.The more I read on the subject (granted it’s
not all from one manufacturer/distributor… I’m reading about all kinds of metal
clays), the more I realized there are so many factors that could contribute to
an unsintered outcome.

Still, I have to try.

Here are some of the things I’m willing to change for my
testing (and showing what my first test will be):

Ramp500°F/hr

Holding Temp 1420

Carbon Under½ inch

Carbon Over½ inch

I’m starting off with Hadar Clay Brilliant Bronze.I’m firing
inside carbon, then letting the pieces cool down to room temperature, then
firing inside carbon a second time.

I’m not going to experiment with holding times.I’m also going to fire in one bowl only
(unless it gives out, then I’ll see what I have that’s similar).I’m not trying different carbons.I am, however, going to start storing my
carbon in an airtight container rather than as it is now which is about five
different bowls of it open to the elements (under a porch).

So here are the pieces I decided upon for my testing.

2-cards thick ¾ x 1½ inch rectangle

4-cards thick ¾ x 1½ inch rectangle

6-cards thick ¾ x 1½ inch rectangle

8-cards thick ¾ x 1½ inch rectangle

12-cards thick ¾ x 1½ inch rectangle

20-cards thick ¼ inch square

This is what they look like before firing. I stamped each one with its card-thickness to make sure I know what's what when I'm testing for strength and sinteredness.

It makes sense to me that difference thicknesses
(and/or different combinations of clays) may require differences in firing
schedules/methods.I hope this testing
leads to some conclusions.Otherwise I’m
wasting a lot of clay.

Phase one is finished and I'm letting the pieces cool (overnight). Check back tomorrow to see the results after the phase two firing.

Did you know that although metal clay is a relatively new
technique to the contemporary jewelry maker (starting in 1990), the
ancient Incas made jewelry from precious metal powders?

BTW, here’s a little internet tool that you can use to help
determine size/shrinkage of various metal clays for pendants and rings.Click here

I don't know how crucial it is that the carbon be in an air tight container, but I was reading an article that mentioned that and I'm thinking, "Geez, my carbon is out there in the elements, gathering moisture (and bugs)." I figure it can't hurt to keep it locked up and if anything it may help.

I've heard of magic carbon, but I haven't used it. I use just one kind and keep it that way to minimize the number of changing factors in the equation.

I use the carbon Hadar recommends. Let me see if I can find out the name... BRB